Acronyms
    FB; Feedlot biomass    CAAA: Clean Air Act Amendments    CCT: Clean Coal Technology    DOE: U.S. Department of Energy    FETC: Federal Energy Technology Center    LNB: low NOx burners    mmBTU: 106 BTU    NOx: Nitrogen Oxides    OFA: overfiered air    SCR: Selective Catalytic Reduction    SNCR: Selective Non-Catalytic Reduction    VOC: volatile organic compounds
NOx is produced when fuel is burned with air. The N in NOx can come either from the N-containing fuel compounds (e.g., Coal) and the N from air. The NOx generated from fuel N is called fuel NOx and that generated from N in air is called thermal NOx. Typically, 75% of NOx is from fuel N. The NOx and volatile organic compounds (VOC's; e.g. gasoline vapors from gas station) released from automobiles, utilities, etc. react in the presence of sun light and produce Ozone or Smog (smoke+fog, 0.08 ppm) which can damage cells in the lung's airways, causing inflammation. Thus the NOx, an ingredient for smog, is proposed to be reduced under title IV of CAAA. Table 1 shows the past regulation of NOx and the proposed new regulations.
TABLE 1Coal-Fired Boiler NOx Emissions Limits (Title IV),ib/million BtuPhase IPhase IIImplementation DateJan. 1, 1996Jan. 1, 2000Group I BoilersDry-Bottom, Wall-Fired0.500.46Tangentially Fired0.450.40Group II BoilersWet-Bottom, Wall-Fired(>65 MWe)NA0.84Cyclone-Fired (>155 MWe)NA0.86Vertically FiredNA0.80Cell BurnerNA0.68Fluidized BedNAExemptStokerNAExempt
The current technologies developed for reducing NOx include: Combustion Controls (e.g., staged combustion, low NOx burners, or reburn technology) and Post Combustion Controls (e.g., Selective Non-Catalytic Reduction, SNCR, etc. using urea). In reburn systems, typically coal or natural gas is injected as an additional fuel downstream of the main burners for reducing the NOx. In SNCR system, Ammonia or urea is injected above the combustion for reducing the NOx. Most current technology uses either coal or natural gas as a reburn fuel coupled with SNCR.
In Frazzitta et al. (Ref. 3), a cofiring experiment using a blend of coal (80%) and cattle manure (feedlot biomass) (20%) is described. Although feedlot biomass contains more N than coal, an increase in NOx was not observed in the experiment. Therefore, the need exists for further exploration and technological development using feedlot biomass as a fuel.